Integrated circuit using topology configurations

ABSTRACT

Various implementations described herein may refer to and may be directed to circuitry for an integrated circuit using topology configurations. For instance, in one implementation, such circuitry may include a memory array having a plurality of memory cells. Such circuitry may also include one or more reconfigurable sense amplifier devices coupled to the memory array and configured to amplify differential voltage levels received from the memory array. The reconfigurable sense amplifier devices may include a plurality of sense amplifier circuits configured to be arranged in one of a plurality of topology configurations, where the topology configurations include a parallel configuration and a cross parallel configuration. The reconfigurable sense amplifier devices may also include one or more switches configured to set the plurality of sense amplifier circuits into the plurality of topological configurations based on one or more control bits.

BACKGROUND

This section is intended to provide information relevant tounderstanding various technologies described herein. As the section'stitle implies, this is a discussion of related art that should in no wayimply that it is prior art. Generally, related art may or may not beconsidered prior art. It should therefore be understood that anystatement in this section should be read in this light, and not as anyadmission of prior art.

Integrated circuits (IC) may be formed from arrangements of one or moreinput/output devices, standard devices, memory devices, and/or the like.In one scenario, memory devices may include memory arrays arranged intomemory cells and the associated circuitry to write data to the memorycells and read data from the memory cells.

In particular, the memory cells of a memory array, such as a randomaccess memory (RAM) array, may be organized into rows and columns. Thelogic latches within these individual memory cells may be used to storea data bit that is representative of a logical “1” or “0.” These memorycells may also be interconnected by word-lines (WL) and pairs ofcomplementary bit-lines (BL).

In a further scenario, one or more sense amplifiers may be connected torespective pairs of complementary bit-lines. A sense amplifier may beused to sense the low power signals swings on a pair of complementarybit-lines, where the power swings represent a data bit stored within anindividual memory cell. The sense amplifier may then amplify the lowpower signal swings to a recognizable logic level, thereby allowing thedata bit to be properly interpreted by logic outside of the RAM array.

In some instances, however, sense amplifiers may be affected by one ormore process variations, which may lead to issues such as the creationof an offset voltage within the sense amplifier. In such instances, theoffset voltage may result in an inaccurate determination of the value ofthe data bit stored within an individual memory cell.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of various techniques will hereafter be described hereinwith reference to the accompanying drawings. It should be understood,however that the accompanying drawings illustrate only variousimplementations described herein and are not meant to limit the scope ofvarious technologies described herein.

FIG. 1 illustrates a block diagram of an embedded memory device inconnection with various implementations described herein.

FIG. 2 illustrates a schematic diagram of a sense amplifier inconnection with various implementations described herein.

FIG. 3 illustrates waveforms for a sense amplifier in connection withvarious implementations described herein.

FIG. 4 illustrates a schematic diagram of a reconfigurable senseamplifier device in accordance with various implementations describedherein.

FIG. 5 illustrates configurations of a reconfigurable sense amplifierdevice in accordance with various implementations described herein.

FIG. 6 illustrates a block diagram of a memory device havingconfiguration bits stored thereon in accordance with variousimplementations described herein.

FIG. 7 illustrates a plot of the probability of error for various senseamplifier configurations in accordance with various implementationsdescribed herein.

FIG. 8 illustrates a schematic diagram of a dual port random-accessmemory (RAM) eight transistor cell in accordance with variousimplementations described herein.

FIG. 9 illustrates a schematic diagram of sense amplifiers coupled topairs of complementary bit-lines in accordance with variousimplementations described herein.

FIG. 10 illustrates a schematic diagram of a reconfigurable senseamplifier device for use with a dual port memory cell in accordance withvarious implementations described herein.

DETAILED DESCRIPTION

Various implementations described herein may refer to and may bedirected to circuitry for an integrated circuit using topologyconfigurations. For instance, in one implementation, such circuitry mayinclude a memory array having a plurality of memory cells. Suchcircuitry may also include one or more reconfigurable sense amplifierdevices coupled to the memory array and configured to amplifydifferential voltage levels received from the memory array. Thereconfigurable sense amplifier devices may include a plurality of senseamplifier circuits configured to be arranged in one of a plurality oftopology configurations, where the topology configurations include aparallel configuration and a cross parallel configuration. Thereconfigurable sense amplifier devices may also include one or moreswitches configured to set the plurality of sense amplifier circuitsinto the plurality of topological configurations based on one or morecontrol bits.

Various implementations of an integrated circuit using topologyconfigurations will now be described in more detail with reference toFIGS. 1-10.

Integrated Circuit

As noted above, integrated circuits (IC) may be formed from arrangementsof one or more input/output devices, standard devices, memory devices,and/or other devices. Input/output devices may be used to providesignals between the connection pins of the IC and the standard devicesand memory devices arranged within the IC. Standard devices may becircuit implementations of flip-flops, arithmetic logic units,multiplexers, retention flops, balloon flops, latches, logic gates,and/or the like. Memory devices may include memory arrays arranged intomemory cells and the associated circuitry to write data to the memorycells and read data from the memory cells.

For example, FIG. 1 illustrates a block diagram of an embedded memorydevice 100 in connection with various implementations described herein.The memory device 100 may include a memory array 105, pre-chargecircuitry 106, row decoder 150, one or more column multiplexers 170, oneor more sense amplifiers 140, and column decoder 160.

In particular, the memory array 105 may be a random-access memory (RAM)array, such as a static RAM (SRAM) array, a dynamic RAM (DRAM) array, acorrelated electron RAM (ceRAM) array, a ferroelectric RAM (feRAM)array, and/or any other implementation known to those skilled in theart. In some implementations, the memory array 105 may be implemented asa single rail memory array, a dual rail memory array, or any other suchimplementation known to those skilled in the art.

The memory array 105 may include a plurality of individual memory cells110, which may be organized in rows 115 and columns 125. As shown inFIG. 1, the array may have N rows and M columns, and, therefore, mayhave N×M individual memory cells 110. As further described below, thesememory cells 110 may include different numbers of transistors (notshown) and may be referred to by the number of transistors. For example,for SRAM arrays, a cell having six transistors may be referred to as asix-transistor or 6-T cell, a cell having eight transistors may bereferred to as an eight-transistor or 8-T cell, and/or the like. Thesetransistors may form a data latch or flip-flop (not shown), which may beused to store a data bit that is representative of a logical “1” or “0”.In further implementations, additional transistors may be added tocontrol access to the latch transistors.

As illustrated in FIG. 1, each row 115 of memory cells 110 may beconnected to at least one of a plurality of word-lines (WL) 120, whereeach word-line 120 may activate a particular row of memory cells 110. Arow decoder 150 may receive address information (e.g., an address word)and then enable the row 115 corresponding to the address word. In someimplementations, each row 115 of memory cells 110 may be used to store aword of data. In other implementations, the row may store part of theword or multiple words, such as a half word or a double word.

Further, each column 125 of memory cells 110 may be connected to atleast one of a plurality of column bit-lines (BL). In oneimplementation, a particular memory cell 110 may be coupled to at leastone pair of complementary bit-lines, such as BLA 132 and BLB 134. Thebit-lines may be used to either store a data bit into a particular cell110 during a write operation, or to read a stored bit from theparticular cell 110 during a read operation. A column decoder 160 mayreceive address information and enable columns 125 corresponding to theaddress. The number of columns 125 activated may depend on the size ofthe word to be stored.

One or more sense amplifiers 140 may be connected to the plurality ofcolumn bit-lines. The inputs of each sense amplifier 140 may be a pairof complementary bit-lines 132, 134 of the memory array 105. The senseamplifier 140 may amplify differential voltage signals between thecomplementary bit-lines 132, 134 of the memory array 105 during a readoperation. These small differential voltage signals may berepresentative of the data bit stored in selected particular individualmemory cell 110, and may be amplified by the sense amplifier 140 to arecognizable logic level to allow the data bit to be properlyinterpreted by logic outside of the memory array 105. Each column 125may be coupled to at least one sense amplifier 140.

In one implementation, one or more column multiplexers 170 may be usedto multiplex the pair of complementary bit-lines in a column 125 into asingle set of sense amplifiers 140, thereby reducing the number of senseamplifiers 140. In another implementation, during periods when there isno read or write operation, the pre-charge circuitry 106 may be enabledto pre-charge the voltage level on the complementary bit-lines 132, 134.

For clarity, FIG. 2 illustrates a schematic diagram of a sense amplifier140 in connection with various implementations described herein. In oneimplementation, the sense amplifier 140 may consist of 2 to 6transistors. In another implementation, the memory device 100 maycontain hundreds or thousands of sense amplifiers 140.

As stated above, during a read operation, the sense amplifier 140 maysense the low power signals between the complementary bit-lines 132,134, which may represent a data bit stored within the individual memorycell 110, and then amplify the small voltage swing to a recognizablelogic level. Upon amplification, the data bit may be latched into abuffer (not shown) and put on an output bus (not shown).

As shown in FIG. 2, bit-line 132 may be coupled to a drain of the pMOSpass-gate transistor M12 and bit-line 134 may be coupled to a drain ofthe pMOS pass-gate transistor M11. The source of pMOS pass-gatetransistor M12 may be coupled to an inverter 230, the output of whichcorresponds to output 232. The source of pMOS pass-gate transistor M11may be coupled to an inverter 234, the output of which corresponds tooutput 236. In addition, the sense amplifier 140 may be enabled via asense amplifier enable (SAE) signal. As shown, the gates of transistorsM12 and M11, along with nMOS transistor M1, may receive the SAE signal.

During a read operation, one of a plurality of word-lines (WL) 120 (notshown) may be enabled. This may lead to a differential voltage on thecomplementary bit-lines 132 and 134. Before the sense amplifier 140 isenabled, the SAE signal may be low. Accordingly, a latch composed of thenMOS transistors M3 and M5 and the pMOS transistors M7 and M9 may nothave a path to VSS. Further, the pMOS pass-gate transistors M12 and M11may couple the voltages of the complementary bit-lines 132 and 134 ontothe internal nodes of the latch.

When the sense amplifier 140 is enabled (i.e., the SAE signal is high),a path to VSS may be activated by way of nMOS transistor M1. Further,the pass-gate transistors M12 and M11 may be disabled, therebydecoupling the internal nodes of the latch from the complementarybit-lines 132 and 134. When the complementary bit-lines 132 and 134 aredecoupled from the internal nodes of the latch, the output of the senseamplifier 140 may be based on the previous differential voltage betweenthe complementary bit-lines 132 and 134.

FIG. 3 illustrates waveforms for a sense amplifier 140 in connectionwith various implementations described herein. In particular, thewaveforms of FIG. 3 illustrate how a sense amplifier 140 may resolve thedifferential signals on the complementary bit-lines 132 and 134 during aread-operation. As shown, the voltage on the bit-line 132 may beslightly lower than the voltage on bit-line 134.

When the sense amplifier 140 is enabled by the signal SAE, the voltageon the internal nodes of the inverter coupled to bit-line 132 may beslightly lower than the voltage on the internal node of the invertercoupled to bit-line 134. Due to the regenerative action of the latches,this difference in voltage may be amplified to a full swing, with thevoltage on the internal node of the inverter coupled to bit-line 132resolving to VSS, and the voltage on the internal node coupled tobit-line 134 resolving to VDD. Therefore, the output 232 of the inverter230 may be high to represent that bit-line 134 is high with respect tobit-line 132.

In some implementations, the sense amplifier 140 may be affected by theprocess variations, such as the lithography process, the fabricationprocess, the packaging process, and/or the like. Such process variationsmay result in a mismatch in the threshold voltages of paired MOSFETswithin the sense amplifier 140, and the creation of an offset voltage.In some instances, the output of the sense amplifier 140 may be based onthe offset voltage as opposed to a differential voltage between thebit-lines 132 and 134. As such, the output of the sense amplifier may beincorrect.

For example, if the sense amplifier 140 has an offset voltage of 60millivolts (mV) and the differential voltage between bit-lines 132 and134 is 40 mV, the sense amplifier 140 may amplify the offset voltage asopposed to the differential voltage. Therefore, the offset voltage ofthe sense amplifier 140 should be smaller than that of the differentialvoltage at the time the sense amplifier 140 is enabled in order for thesense amplifier 140 to accurately determine the content of the data bitwithin the memory cell 110.

The process variations which may cause such an offset voltage mayinclude local variations and global variations. Local variations, orintra-die variations, may be attributable to variations in line edgeroughness and random dopant fluctuations in the Metal OxideSemiconductor Field Effect Transistor (MOSFET) channel. Random dopantfluctuations may be process related, and may be the result of variationsin the implanted impurity concentration. As integrated circuits arescaled down in size, these dopant fluctuations may become significant,as the number of dopants atoms in the MOSFET channel may beproportionally fewer. This local variation may enhance the asymmetry ofpaired MOSFETS within ratio devices, such as a sense amplifier 140discussed herein, and therefore its offset voltage. Global variations ofthese process variations, or die-to-die variation, may be attributableto variations of the MOSFET channel length (L_(g)), MOSFET channel width(W), dopant channel concentrations, and/or gate oxide thickness.

Further, other devices and/or circuitry of the integrated circuit, suchas those related to memory devices, may be affected by theabove-described process variations, such as through the creation ofoffset voltages in these other devices and/or circuitry. For example,process variations may result in memory cells 110 that are weaker and,in turn, able to generate less differential voltage on the complementarybit-lines 132 and 134. If a memory array 105 cannot correctly identifythe information contained in the cell 110, then it may not be able tofunction as an embedded memory device within the integrated circuit,thereby reducing the yield of the integrated circuit.

Integrated Circuit Using Multiple Topologies

To mitigate the effects of process variations in ICs, which may lead tooffset voltages as described above, the devices and/or circuitry of theICs may be configured into one of a plurality of topologies. Such animplementation may allow for the reduction of offset voltage in the IC,since a topology which exhibits the least amount of offset voltage canbe selected from the plurality of topologies.

For example, and as further described below, sense amplifiers used in amemory device of an IC may be reconfigured into one of a plurality oftopologies, where the topologies may include a parallel topology and/ora cross-parallel topology. It should be noted, however, that theimplementations described below may be used for other devices and/orcircuitry of ICs exhibiting mismatch due to processing variations, suchas operational amplifiers, instrumentation amplifiers, timers, voltageand current regulators, filters, sensors, switches, transducers, digitalto analogue converters (DAC), analogue to digital converters (ADC),and/or the like.

Reconfigurable Sense Amplifier

FIG. 4 illustrates a schematic diagram of a reconfigurable senseamplifier device 400 in accordance with various implementationsdescribed herein. As further described below, the reconfigurable senseamplifier device 400 may be placed into one of a plurality of differenttopologies.

The reconfigurable sense amplifier device may include a plurality ofsense amplifier circuits, such as sense amplifier 140 described above.As shown, the device 400 may include two sense amplifiers, senseamplifier 1 (SA1) 410 and sense amplifier 2 (SA2) 420, which may besimilar to the sense amplifier 140. While only two sense amplifiers areillustrated, it will be understood by a person skilled in the art thatmore than two may be used. In another implementation, the senseamplifiers of the device 400 may be selected from one or more commonpools of sense amplifiers, with the number of sense amplifiers and theirconfigurations being determined by factors such as: the voltage offsetof the individual sense amplifiers, their location within the integratedcircuit, and the speed, power distribution, and yield of memory arraysand/or IC.

In one implementation, the functionality of the SA1 410 and SA 420 maybe the same. In a further implementation, the circuitry for SA1 410 andSA2 420 may also be the same. However, for other implementations, itwill also be understood by a person skilled in the art that while thefunctionality of the SA1 410 and SA 420 may be the same, the circuitryfor implementing that functionality may be different.

In one implementation, SA1 410 and SA 420 may be substantially the samesize. In another implementation, SA1 410 and SA2 420 may be of adifferent size. For example, SA2 420 may be physically larger than SA1410, whereby SA1 410 may be used to obtain minimum power dissipationwhile SA2 420 may be used to obtain absolute yield and/or performance.In a further implementation, the relative scaling of SA1 410 and SA2 420may be non-linear, depending on the process technology, the standarddeviation of the manufacturing variances, and/or combination thereof. Assuch, scaling may increase or decrease the absolute size of theindividual sense amplifiers and/or their individual components. Scalingmay also be determined by other factors known to a person of ordinaryskilled in the art.

As shown in FIG. 4, the reconfigurable sense amplifier device 400 mayinclude a plurality of pMOS pass-gate transistors M12 and M11. The drainof the pMOS pass-gate transistor M12 may be coupled to bit-line 132 andthe drain of the pMOS pass-gate transistor M11 may be coupled tobit-line 134. The source of pMOS pass-gate transistor M12 may be coupledto an inverter 230, the output of which corresponds to output 232. Thesource of pMOS pass-gate transistor M11 may be coupled to an inverter234, the output of which corresponds to output 236.

The node corresponding to the source of pMOS pass-gate transistor M12may be referred to as “node 3”, and the node corresponding to the sourceof pMOS pass-gate transistor M11 may be referred to as “node 3 ”.Further, the node corresponding to the junction of the latch composed ofnMOS transistor M5 and pMOS transistor M9 of SA2 420 may be referred toas “node 2”. The node corresponding to the junction of the latchcomposed of nMOS transistor M3 and pMOS transistor M7 may be referred toas “node 2 ”. The node corresponding to the junction of the latchcomposed of nMOS transistor M6 and pMOS transistor M10 of SA1 410 may bereferred to as “node 1”. In addition, the node corresponding to thejunction of the latch composed of nMOS transistor M4 and pMOS transistorM8 may be referred to as “node 1 ”.

Further, the reconfigurable sense amplifier device 400 may also includea plurality of pass-gate switches. In one implementation, the device 400may include three pairs of switches (sense amplifier switches): SW1 480and 482, SW2 484 and 486, and SW3 488 and 490. In such animplementation, SW1 480 may be positioned between node 1 and node 3, SW1482 may be positioned between node 1 and node 3 , SW2 484 may bepositioned between node 2 and node 3, SW2 486 may be positioned betweennode 2 and node 3 , SW3 488 may be positioned between node 2 and node 3, and SW3 490 may be positioned between node 2 and node 3 .

In operation, based on the statuses of the pass-gate switches, thereconfigurable sense amplifier device 400 may transition among one offour possible reconfigurable topologies. Those reconfigurable topologiesinclude: 1) a configuration that uses only SA1 410; 2) a configurationthat uses only SA2 420; 3) a configuration that uses both SA1 410 andSA2 420, where SA1 410 and SA2 420 are directly connected and inparallel (denoted as “SA1+SA2”); and 4) a configuration that uses bothSA1 410 and SA2 420, where SA1 410 and SA2 420 are cross connected andin cross parallel (denoted as “SA1−SA2”). For the SA1−SA2 configuration,SA1 and SA2 are connected in parallel but with the inputs of SA2 420swapped for one another. In a further implementation, the number ofsense amplifiers may be greater than two, and there may be additionaland/or alternative configurations. For example, there may be three senseamplifiers, and they may be configured such that two are in parallel andthe third is in cross parallel.

With respect to the reconfigurable sense amplifier device 400, thevarious topology configurations may be determined based on the pairs ofpass-gate switches: SW1 480 and 482, SW2 484 and 486, and SW3 488 and490. In particular, a specific combination of activated pass-gateswitches may place the reconfigurable sense amplifier device 400 intoone of the possible reconfigurable topologies.

For example, FIG. 5 illustrates configurations of the reconfigurablesense amplifier device 400 in accordance with various implementationsdescribed herein. As shown, the SA1 configuration may be selected ifonly SW1 480 and 482 are activated. The SA2 configuration may beselected if only SW2 484 and 486 are activated. The SA1+SA2configuration may be selected if only SW1 480, 482 and SW2 484, 486 areactivated. The SA1−SA2 configuration may be selected if only SW1 480,482 and SW3 488, 490 are selected.

To activate particular pass-gate switches, one or more control bits maybe used. For example, as shown in FIG. 4, one of the four reconfigurabletopologies may be determined using control bits C1 and C2 and one ormore corresponding logic functions. In particular, a NAND operation onthe control bits may be used to activate switches SW1 480 and 482, and aNOR operation on the control bits may be used to activate switches SW3488 and 490. Switches SW2 484 and 486 may correspond directly to bit C1.Accordingly, the control bits may be used to select a particulartopology configuration of the reconfigurable sense amplifier device 400.Other implementations of control bits and/or logic functions may be usedto activate the switches and, in turn, select a particular topologyconfiguration.

In one implementation, the control bits may be written into memory. Forexample, FIG. 6 illustrates a block diagram of a memory device 600having configuration bits stored thereon in accordance with variousimplementations described herein. The memory device 600 may be similarto that of memory device 100, in that it includes a memory array 105,row decoder 150, one or more column multiplexers (not shown), and one ormore reconfigurable sense amplifier devices 400. The memory array 105may include a plurality of memory cells 110, which may be organized intorows 115 and columns 125.

As shown in FIG. 6, control bits C1 and C2 may be written to twoindividual memory cells 110 of the last row of the array 105. Inconjunction with 2:1 column multiplexing, the control bits may be storedimmediately above the sense amplifiers SA1 410 and SA2 420. In oneimplementation, due to the proximity of SA1 410 and SA2 420, the controlbits may be directly hard-wired to the storage nodes of the senseamplifiers using fuses. In another implementation, values of the controlbits may be determined using a calibration process and/or Built-InSelf-Test (BIST). In yet another implementation, there may be no columnmultiplexing, and the control bits C1 and C2, may be stored in theindividual cells of the last two rows 115 of the array 105.

Referring back to FIG. 4, the control bits, C1 and C2, and the pairs ofpass-gate switches, SW1 480 and 482, SW2 484 and 486, and SW3 488 and490, may be used to implement the various topologies of thereconfigurable sense amplifier device 400. Having a configuration thatuses only SA1 410 and a configuration that uses only SA2 420 may createredundancies for the individual sense amplifiers in the device 400. Inaddition, having the SA1+SA2 configuration and the SA1−SA2 configurationmay create additional redundancies for implementing sense amplifiers inan IC. In another implementation, SA1 410 and SA2 420 may periodicallyhave a path to VSS even though one of them may not be utilized based onan implemented topology. In a further implementation, additionalcircuitry and/or logic may be implemented such that SA1 410 and/or SA2420 are enabled only during a read-operation when utilized by aparticular topology.

Each of the four possible reconfigurable topologies may have aparticular offset voltage associated with it. Specifically, theconfiguration that uses only SA1 410 may have an offset voltage of V1;the configuration that uses only SA2 420 may have an offset voltage ofV2; 3) the SA1+SA2 configuration may have an offset voltage of(V1+V2)/2; and 4) the SA1−SA2 configuration may have an offset voltageof (V1−V2)/2. For the SA1+SA2 and SA1−SA2 configurations, the totaloffset voltage of the device 400 is the average of the individualvoltage offsets of SA1 and SA2. Therefore, the individual offsetvoltages may compensate each other when they have the opposite sign ormay be added together when they have the same sign.

Thus, the reconfigurable structure of the reconfigurable sense amplifierdevice 400 has the capability to: 1) allow each of the SA1 410 and SA2420 to be individually connected and/or disconnected, and/or 2)individually maintain or swap two of the differential inputs for SA1 410and SA2 420. As shown in FIG. 4, SA2 420 is configured to have itsdifferential inputs swapped. In one implementation, circuitry may alloweach of the differential inputs of both sense amplifiers to be swapped.Therefore, the reconfigurable structure of the device 400 allows: 1) theindividual voltage offset contribution of each of the sense amplifiers,SA1 410 and SA2 420, to be included or excluded, and/or 2) the polarityof each of the voltage offsets of SA1 410 and SA2 420 to be maintainedand combined, and/or 3) the polarity of SA2 420 voltage offset to beinverted, and combined with that of SA1 410.

In one implementation, after fabrication, values for the control bitsmay be selected by a controller, such that the topology having thesmallest offset voltage is the implemented topology in device 400. Inanother implementation, certain topologies may have a higher probabilityof resulting in a lower offset voltage. For example, theseconfigurations may be the parallel SA1+SA2 and cross-parallel SA1−SA2configurations. In a further implementation, this characteristic may beexploited to reduce the number of control bits and pairs of pass-gateswitches. For example, in such an implementation, only the parallelSA+SA2 and cross-parallel SA1−SA2 topology configurations may beimplemented. Accordingly, the device 400 may only use a single controlbit and two pairs of pass-gate switches, SW1 480, 482 and SW3 488, 490.

As discussed above, positioning two or more sense amplifiers in parallelor cross parallel within the area of device 400 may lead to a reducedoffset voltage when compared to using a single sense amplifier withinthe same area. Such a reduction in offset voltage for the reconfigurablesense amplifier device 400 can be theoretically shown by simplestatistical analysis as follows. Assuming a normal distribution, N(0,1),(σ_(Conv)=1) for a sense amplifier within a predefined area. If thepredefined area is then divided to accommodate k smaller senseamplifiers, each will have, according to Pelgrom's model, √{square rootover (k)} times larger standard deviation, as shown below:σ_(SmallSA) =√{square root over (k)}σ _(Conv)  Equation 1.

By putting two of these smaller sense amplifiers in parallel, the totaloffset will be the average of the two sense amplifiers offset voltages,which yields another Gaussian distribution with standard deviation of:σ_(Parallel) _(_) _(SmallSA)=(√{square root over(k/2)})σ_(Conv)  Equation 2.

The probability of error of the individual redundancy may then be:Pr(Error)=Pr(SmallSA _(Offset) >Vin)²  Equation 3.

The probability of error of the Pos-Neg Redundancy may then be:Pr(Error)=Pr(Parallel_SmallSA _(offset) >Vin)²  Equation 4.

The probability of error of the Reconfigurable SA may then be:Pr(Error)=Pr(SmallSA _(offset) >Vin)² ·Pr(Parallel_SmallSA _(offset)>Vin)²  Equation 5

FIG. 7 illustrates a plot 700 of the probability of error for varioussense amplifier configurations in accordance with variousimplementations described herein. The plot may have a fixed differentialinput (5.73σ_(Conv), translating to an error probability of 1-e8) forthe conventional sense amplifier 140, individual redundancy SA1 and SA2,parallel SA1+SA2 and cross parallel SA1-SA2. As can be seen from FIG. 7,the use of a reconfigurable sense amplifier device 400 considerablyreduces the probability of error even within a smaller total die area.

Referring to FIG. 7, a reconfigurable sense amplifier device 400 may beused to obtain a statistically lower voltage offset within a given diearea as compared to a single sense amplifier 140 of substantiallycomparable size. Therefore, the reconfigurable sense amplifier device400 may be used to improve the absolute yield of embedded memory arrays105, to improve the speed of embedded memory arrays 105, to reduce thepower dissipation within the embedded memory arrays 105, and/orcombinations thereof. In this manner, the use of various reconfigurabletopologies may be used to obtain substantially the same offset voltageperformance as a single sense amplifier 140 within a smaller die area.As mentioned above, the reconfigurable sense amplifier device 400 mayinclude more than 2 sense amplifiers. The number of topologyconfigurations and/or configurations bits may increase accordingly withthe number of sense amplifiers. In one implementation, thischaracteristic may be exploited to reduce or optimize the calibrationtime for a particular reconfigurable topology to be selected. Forexample, the calibration process may start with the topologyconfiguration and/or configurations that statistically have the highestprobability of minimizing the voltage offset of the sense amplifier, andthen terminate once a topology configuration has been tested thatsatisfies the required performance without testing the remainingconfigurations. In another implementation, the calibration process maybe used to batch select (i.e., grade) sense amplifiers 140 and thereforethe embedded memory arrays and integrated circuits. For example, thenumber of configurations tested, and therefore the total calibrationtime, may be increased to establish a higher yield and/or grade ofintegrated circuits.

The performance for the reconfigurable sense amplifier device 400 may bedetermined by a number of factors. For example, a minimum offset voltagemay depend on a supply voltage that the integrated circuit and thememory arrays 105 are designed to operate at and/or whether the supplyvoltage is regulated or unregulated. Despite large variations inthreshold voltage between match pair devices within the sense amplifier140, the sense amplifier 140 may still be electrically stable whileoperating at these low supply voltages. Therefore, to ensure this higherperformance requirement can be satisfied, more configurations may betested.

The performance may also depend on the energy management architecture ofthe integrated circuit, which may include sleep/hibernation power savingmodes. In one implementation, there may be more topology configurationsand/or configurations tested during calibration for sense amplifiersthat have to sense data bits and/or dissipated minimum power insleep/hibernation mode. For example, in sleep/hibernation mode, some ofthe memory array 105 may be on a switched supply rail that is isolatedduring sleep/hibernation mode, and/or the supply voltage may be loweredto reduce power dissipated as part of a power saving energy managementfunction. As such, the number of topology configurations and/or thecalibration processes may vary depending on the sense amplifiers'physical location within the integrated circuit.

The performance of the reconfigurable sense amplifier device 400 mayalso depend on the system timing and/or expected operating temperatureof the integrated circuit and the memory array 105. The latter maydepend on the device packaging, which may vary.

As stated above, the reconfigurable sense amplifier device 400 may beused to improve the absolute yield and/or performance, and/or to obtaina given performance within a smaller die area than an equivalentconventional single sense amplifier 140.

Integrated Circuit Using Dual Port Memory Cells

In some implementations, the memory cell 110 as described above may beimplemented as a single port memory cell, a dual port memory cell, orany other such implementation known to those skilled in the art. Forexample, the memory cell 110 may be a dual port memory cell, such as aneight-transistor (8-T) memory cell.

FIG. 8 illustrates a schematic diagram of a dual port 8-T memory cell810 in accordance with various implementations described herein. Thememory cell 810 may include two sets of word-lines and data ports. Inone implementation, the memory cell 810 may be similar to the memorycells disclosed in U.S. Pat. No. 8,582,389, which is herein incorporatedby reference. In addition, the memory cell 810 may be part of a memoryarray similar to memory array 105 as described above.

As shown in FIG. 8, the memory cell 810 may include pMOS pull-uptransistors PUL and PUR and nMOS pull-down transistors PDL and PDR.Pass-gate transistors PGLA and PGRA may form a first port (port-A) 822of the memory cell 810. Pass-gate transistors PGLB and PGRB may form asecond port (port-B) 824 of the memory cell 810. The gates of pass-gatetransistors PGLA and PGRA may be controlled by the word-line (WLA) atport-A, while the gates of pass-gate transistors PGLB and PGRB may becontrolled by the word-line (WLB) at port-B. A latch composed of thepull-up transistors PUL and PUR and pull down transistors PDL and PDRmay store a data bit. The stored data bit can be read through port-Ausing a first pair of complementary bit-lines 880 and 882. The storeddata bit can also be read through the port-B 824 using a second pair ofcomplementary bit-lines 884 and 886.

In one implementation, in response to a read request, data may be readout of the memory cell 810 using either the first pair or the secondpair of bit-lines, depending on which of WLA or WLB is activated. Inparticular, based on the configuration of the pass-gate transistors PGLAand PGRA, data may be read out of the first pair of bit-lines if WLA isactivated, whereas, based on the configuration of the pass-gatetransistors PGLB and PGRB, data may be read out of the second pair ofbit-lines if WLB is activated.

In such an implementation, during a read operation, data may be read outof the memory cell 810 using either the first pair or the second pair ofbit-lines, but not both pairs of bit-lines. Accordingly, during a readoperation, only one of WLA or WLB may be activated, but not both. Suchselective activation of the word-lines may be used to mitigate effectsof read disturb of the memory cell 810.

In particular, during a read operation, the first pair and the secondpair of bit-lines may operate independently of each other, such that thefirst pair and the second pair of bit-lines may be isolated from oneanother. This is in contrast to some implementations where the first andthe second pair of bit-lines may operate in conjunction with one anotherduring certain write operations, as discussed, for example, in U.S. Pat.No. 8,582,389. In a further implementation, only one of the first pairor the second pair of bit-lines may be precharged. In particular, onlythe pair of bit-lines to be used during the read operation may beselected for precharging. Such selective precharging may be used for lowvoltage operations.

In such implementations where data is read out only one of the firstpair and the second pair of bit-lines, the selection of which of thepairs of bit-lines to use during the read operation may be based onwhich pair provides the better readability. Readability may depend onfabrication variations, where such variations may include some pass-gatetransistors having different current outputs than other pass-gatetransistors of the memory cell, metal mismatch between port-A andport-B, current changes in the transistors of the memory cell due tocapacitance on the pairs of bit-lines, and/or any other fabricationvariation known to those skilled in the art. Accordingly, the redundantuse of dual pairs of bit-lines with the memory cell 810 may allow for anoptimal selection of bit-lines for use during a read operation.

In a further implementation, the first pair of complementary bit-lines880 and 882 and the second pair of complementary bit-lines 884 and 886may each be coupled to sense amplifiers, such as the sense amplifiers140 discussed above with respect to FIGS. 1 and 2.

For example, FIG. 9 illustrates a schematic diagram 900 of senseamplifiers coupled to pairs of complementary bit-lines in accordancewith various implementations described herein. As shown, the first pairof complementary bit-lines 880 and 882 may transmit data to a firstsense amplifier 910, and the second pair of complementary bit-lines 884and 886 may transmit data to a second sense amplifier 920. In oneimplementation, the first sense amplifier 910 and the second senseamplifier 920 may be identical or substantially identical. Further, a2-to-1 multiplexer 930 may be used to select which of the senseamplifier outputs is to be transferred to other circuitry of the IC.

In one implementation, the multiplexer 930 may be used to select thesense amplifier output corresponding to the pair of bit-lines thatprovides the better readability, as discussed above. In anotherimplementation, the multiplexer 930 may be used to select the senseamplifier output corresponding to the sense amplifier having the leasteffects related to process variations, such as the sense amplifierhaving the least amount of offset voltage. Accordingly, the redundantuse of dual pairs of bit-lines and/or the substantially identical senseamplifiers with the memory cell 810 may allow for an optimal selectionof bit-lines and/or sense amplifiers for use during a read operation ofthe memory cell 810.

FIG. 10 illustrates a schematic diagram of a reconfigurable senseamplifier device 1000 for use with the dual port memory cell 810 inaccordance with various implementations described herein. The device1000 may be similar to the reconfigurable sense amplifier device 400 asdiscussed above with respect to FIG. 4. In particular, the device 1000may include sense amplifier SA1 410 and sense amplifier SA2 420, withcircuitry and various topology configurations and redundancy asdetermined by the three pairs of switches (sense amplifier switches):SW1 480 and 482, SW2 484 and 486, and SW3 488 and 490.

In addition, the device 1000 may further include a plurality of bit-linepass-gate switches. In particular, the device 1000 may include two pairsof bit-line pass-gate switches: 1) SW4 1010 and 1012, and 2) SW5 1014and 1016. As shown, SW4 1010 and 1012 may be used to couple the firstpair of complementary bit-lines 880 and 882 to the reconfigurable senseamplifier device 1000, while SW5 1014 and 1016 may be used to couple thesecond pair of complementary bit-lines 884 and 886 to the reconfigurablesense amplifier device 1000.

As similarly discussed above, data may be read out of a dual port memorycell (not shown) using either pair of bit-lines coupled to thereconfigurable sense amplifier device 1000, but not both pairs ofbit-lines. In particular, the bit-line pass-gate switches SW4 or thebit-line pass-gate switches SW5 may be used to couple one pair ofbit-lines to the reconfigurable sense amplifier device 1000. In such animplementation, the bit-line pass-gate switches may be used to coupleone pair of bit-lines to the pass-gate transistors of the reconfigurablesense amplifier device 1000 (i.e., PGLA and PGRA or PGLB and PGRB).

As shown, and as discussed above, these bit-line pass-gate switches maybe used to exploit the redundant use of dual pairs of bit-lines with thedual port memory cell 810 by allowing for an optimal selection ofbit-lines for use during a read operation of the cell 810. Inparticular, the bit-line pass-gate switches may be used to select thepair of bit-lines having the better readability. As discussed above withrespect to FIG. 8, readability may depend on fabrications variationsand/or the like.

In one implementation, the various topology configurations of device1000 may be determined by an additional configuration bit C3 (not shown)and corresponding logic functions (not shown). In a furtherimplementation, the configuration bit C3 may be stored in a memory arrayin a manner similar to that described herein with respect to the storageof C1 and C2. In another implementation, the topology configurationchosen may be determined by a calibration test and/or BIST function.This calibration test and/or BIST function may be used to determinewhich topology configuration leads to the optimal performance and/orhighest yield for the embedded memory array during a read-operation.

In another implementation, the redundancy in the dual port memory cell810 read circuitry may be combined with a reconfigurable sense amplifierdevice 400. Further, the number of sense amplifiers is not limited tojust two, and the number of topology configurations and/orconfigurations bits may increase accordingly. In a furtherimplementation, the control bits and a control circuitry may becombined.

It should be understood by a person of ordinary skill in the art thatwhile the various implementations and accompanying drawings describedherein have been with specific reference to sense amplifiers withinembedded RAM memory arrays of mixed-signal integrated circuits, they arenot limited to such. It should be understood by a person of ordinaryskill in the art that various implementations, apparatus, processes andmethods described herein are applicable to any integrated circuit,wherein comparable components and/or devices exhibit mismatch that arethe result of local and/or global manufacturing variations. Further, itwill be understood that these manufacturing variations may be attributedto the lithography process, the fabrication process, the packagingprocess, and/or any other manufacturing variations known to a person ofordinary skilled in the art. As such, various implementations describedherein will be understood to be applicable not only to sense amplifierswithin mixed-signal integrated circuits such as memories, but othermixed-signal integrated circuits such as digital to analog converters(DAC), analog to digital converters (ADC), analog integrated circuits,operation amplifiers, an instrumentation amplifiers, timers, voltage andcurrent regulators, filters, sensors, switches, transducers, and/or thelike.

The discussion provided herein is directed to certain specificimplementations. It should be understood that the discussion providedherein is provided for the purpose of enabling a person with ordinaryskill in the art to make and use any subject matter defined herein bythe subject matter of the claims.

It should be intended that the subject matter of the claims not belimited to the implementations and illustrations provided herein, butinclude modified forms of those implementations including portions ofimplementations and combinations of elements of differentimplementations in accordance with the claims. It should be appreciatedthat in the development of any such implementation, as in anyengineering or design project, numerous implementation-specificdecisions should be made to achieve a developers' specific goals, suchas compliance with system-related and business related constraints,which may vary from one implementation to another. Moreover, it shouldbe appreciated that such a development effort may be complex and timeconsuming, but would nevertheless be a routine undertaking of design,fabrication, and manufacture for those of ordinary skill having benefitof this disclosure.

Reference has been made in detail to various implementations, examplesof which are illustrated in the accompanying drawings and figures. Inthe detailed description, numerous specific details are set forth toprovide a thorough understanding of the disclosure provided herein.However, the disclosure provided herein may be practiced without thesespecific details. In some other instances, well-known methods,procedures, components, circuits and networks have not been described indetail so as not to unnecessarily obscure details of the embodiments.

It should also be understood that, although the terms first, second,etc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are only used todistinguish one element from another. For example, a first element couldbe termed a second element, and, similarly, a second element could betermed a first element. The first element and the second element areboth elements, respectively, but they are not to be considered the sameelement.

The terminology used in the description of the disclosure providedherein is for the purpose of describing particular implementations andis not intended to limit the disclosure provided herein. As used in thedescription of the disclosure provided herein and appended claims, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. The term“and/or” as used herein refers to and encompasses any and all possiblecombinations of one or more of the associated listed items. The terms“includes,” “including,” “comprises,” and/or “comprising,” when used inthis specification, specify a presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components and/or groups thereof.

As used herein, the term “if” may be construed to mean “when” or “upon”or “in response to determining” or “in response to detecting,” dependingon the context. Similarly, the phrase “if it is determined” or “if [astated condition or event] is detected” may be construed to mean “upondetermining” or “in response to determining” or “upon detecting [thestated condition or event]” or “in response to detecting [the statedcondition or event],” depending on the context. The terms “up” and“down”; “upper” and “lower”; “upwardly” and “downwardly”; “below” and“above”; and other similar terms indicating relative positions above orbelow a given point or element may be used in connection with someimplementations of various technologies described herein.

While the foregoing is directed to implementations of various techniquesdescribed herein, other and further implementations may be devised inaccordance with the disclosure herein, which may be determined by theclaims that follow. Although the subject matter has been described inlanguage specific to structural features and/or methodological acts, itis to be understood that the subject matter defined in the appendedclaims is not necessarily limited to the specific features or actsdescribed above. Rather, the specific features and acts described aboveare disclosed as example forms of implementing the claims.

What is claimed is:
 1. An integrated circuit, comprising: a memoryarray, comprising a plurality of memory cells; and one or morereconfigurable sense amplifier devices coupled to the memory array andconfigured to amplify differential voltage levels received from thememory array, the one or more reconfigurable sense amplifier devicescomprising: a plurality of sense amplifier circuits configured to bearranged in one of a plurality of topology configurations, wherein thetopology configurations comprise a parallel configuration and a crossparallel configuration; and one or more switches configured to set theplurality of sense amplifier circuits into the plurality of topologicalconfigurations based on one or more control bits.
 2. The integratedcircuit of claim 1, wherein the switches comprise one or more pass-gateswitches driven by the one or more control bits.
 3. The integratedcircuit of claim 2, wherein the one or more pass-gate switches aredriven by the one or more control bits in conjunction with one or morecombinational logic circuits.
 4. The integrated circuit of claim 1,wherein the control bits are configured to arrange the plurality ofsense amplifier circuits into a topology configuration having a leastamount of offset voltage.
 5. The integrated circuit of claim 1, whereinthe one or more control bits are stored in one or more of the memorycells.
 6. The integrated circuit of claim 1, wherein a total offsetvoltage of the one or more reconfigurable sense amplifier devices in aparticular topology configuration comprises an average of individualoffset voltages of the plurality of sense amplifier circuits used in theparticular topology configuration.
 7. The integrated circuit of claim 1,wherein the plurality of sense amplifier circuits comprise a first senseamplifier circuit and a second sense amplifier circuit, and wherein theone or more switches are configured to set the first sense amplifiercircuit and the second sense amplifier circuit into one of four topologyconfigurations.
 8. The integrated circuit of claim 7, wherein the fourtopology configurations comprise: a first configuration using the firstsense amplifier circuit; a second configuration using the second senseamplifier circuit; a third configuration using the first sense amplifiercircuit and the second sense amplifier circuit, wherein the first senseamplifier circuit and the second sense amplifier circuit are directlyconnected and in parallel; and a fourth configuration using the firstsense amplifier circuit and the second sense amplifier circuit, whereinthe first sense amplifier circuit and the second sense amplifier arecross connected and in cross parallel.
 9. The integrated circuit ofclaim 1, further comprising: a first bit-line pair coupled to arespective memory cell of the memory array and to a respectivereconfigurable sense amplifier device; and a second bit-line paircoupled to the respective memory cell and to the respectivereconfigurable sense amplifier device, wherein, during a read operationof the respective memory cell, the first bit-line pair or the secondbit-line pair is selected to transmit data stored within the respectivememory cell based on a readability of the first bit-line pair and thesecond bit-line pair.
 10. The integrated circuit of claim 9, furthercomprising: a first set of bit-line switches configured to couple thefirst bit-line pair to the respective reconfigurable sense amplifierdevice; and a second set of bit-line switches configured to couple thesecond bit-line pair to the respective reconfigurable sense amplifierdevice, wherein the first bit-line pair or the second bit-line pair isselected using the first set of bit-line switches and the second set ofbit-line switches.